1. Field of the Invention
The present invention relates to a radiographic image display device and method for displaying a stereo image of a subject.
2. Description of the Related Art
In an examination at a hospital, a piece of tissue around the lesion may be collected. In recent years, as a method for collecting a piece of tissue without putting a large burden on the patient, a biopsy to puncture the patient with a hollow needle for tissue collection (hereinafter, referred to as a biopsy needle) and collect the tissue embedded in the cavity of the needle has been drawing attention. In addition, a stereo biopsy device has been proposed as a device for performing such a biopsy.
This stereo biopsy device is intended to acquire a plurality of radiographic images with parallax by irradiating a subject from different directions and display a stereo image based on these radiographic images. Since a three-dimensional position of a lesion can be specified while observing the stereo image, a piece of tissue can be collected from a desired position by controlling the tip of the biopsy needle to reach the specific position.
Meanwhile, in the medical field, a computer aided image diagnosis system (CAD: computer aided diagnosis) to automatically detect an abnormal shadow in an image and perform highlighting or the like of the detected abnormal shadow is known. A doctor interprets the image including the abnormal shadow detected by the CAD system, and finally determines whether or not the abnormal shadow in the image is an abnormal shadow indicating a lesion, such as a tumor or calcification.
As a method for detecting an abnormal shadow, for example, a method for automatically detecting the candidate of a tumor shadow (a form of an abnormal shadow), which is a form of cancer or the like, by performing image processing on a radiographic image of the breast or chest using an iris filter and performing thresholding of the output value (refer to JP1998-97624A (JP-H10-97624A)) or a method for automatically detecting the candidate of a micro-calcification shadow (a form of an abnormal shadow), which is another form of breast cancer or the like, by performing image processing using a morphology filter and performing thresholding of the output value (refer to JP 1996-294479A (JP-H08-294479A)) is known.
Incidentally, since the radiographic image is a transmission image inside the subject, structures, such as bones, various tissues, and lesions including tumors or calcification, inside the subject are included in the radiographic image in a state overlapping each other. For this reason, when displaying a stereo image of the radiographic image, an instruction, such as designating an abnormal shadow, is given on the stereo image using a three-dimensional cursor that can move not only in a planar direction but also in a depth direction.
Here, in order to make it easier to visually recognize the detected abnormal shadow, a method for automatically giving a mark, such as an arrow, to the abnormal shadow has been proposed (refer to JP2007-215727A). In addition, a method for giving a mark, such as an arrow, to the abnormal shadow detected by CAD in a plurality of radiographic images for displaying a stereo image and specifying an abnormal shadow of the other image corresponding to the abnormal shadow designated in one image and also giving a warning when an abnormal shadow cannot be detected in the other image has been proposed (refer to JP2010-137004A). In addition, a method for detecting an abnormal shadow from a plurality of radiographic images for three-dimensional display and giving a mark stereoscopically by giving parallax to the plurality of radiographic images when giving a mark such that the detected abnormal shadows match each other has been proposed (refer to JP2004-337200A).
When a plurality of abnormal shadows are detected from radiographic images for displaying a stereo image, a stereo image can be displayed together with marks by giving the marks to the plurality of abnormal shadows using the methods disclosed in JP2010-137004A and JP2004-337200A. Here, when designating an abnormal shadow using a three-dimensional cursor instead of a mark, the operator needs to match the position of the abnormal shadow in the depth direction with the position of the abnormal shadow in the planar direction. However, matching the sense of depth of the three-dimensional cursor with the sense of depth of the abnormal shadow in a stereo image is very troublesome work.
In particular, in the case of stereo biopsy, the stereoscopic effect of a stereo image is larger than the stereoscopic effect of a normal stereo image. Therefore, continuously watching such a stereo image with a large stereoscopic effect in order to match the stereoscopic effect of the three-dimensional cursor with the stereoscopic effect of the abnormal shadow makes the eyes of the operator very tired.
In addition, in the method disclosed in JP2004-337200A, when matching the detected abnormal shadows between radiographic images, abnormal shadows that do not correspond to each other geometrically are eliminated in consideration of the parallax between the radiographic images. Then, the minimum value of the distance between the detected abnormal shadows is calculated between the radiographic images, and abnormal shadows that can be regarded as the most equal abnormal shadows based on the minimum value are matched with each other.
However, in the method disclosed in JP2004-337200A, as shown in FIG. 10, when abnormal shadows B1 and B2 are present, they are included as abnormal shadows BL1 and BL2 and abnormal shadows BR1 and BR2 in a radiographic image for a left eye GL and a radiographic image for a right eye GR acquired at two radiation source positions PL and PR, respectively. If the positions of the abnormal shadows B1 and B2 in a direction perpendicular to the plane (Y direction) are the same, however, it is not possible to specify to which of the abnormal shadows BR1 and BR2 the abnormal shadow BL1 corresponds and to which of the abnormal shadows BR1 and BR2 the abnormal shadow BL2 corresponds on the image.
Thus, unless abnormal shadows can be matched with each other, the same mark cannot be given to corresponding abnormal shadows. In particular, in a stereo biopsy, the tip of the biopsy needle cannot be made to reach the position of the abnormal shadow accurately.